Thermo-responsive solution, and method of use therefor

ABSTRACT

The present invention relates to a thermo-responsive solution and in particular, a solution for use in an osmosis process that is suitable for separating or purifying solutes and or water from an aqueous solution on a large scale and under energy efficient conditions.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/338,076, filed Mar. 29, 2019, which is a 35 U.S.C. 371 national stagefiling of International Application No. PCT/NZ2017/050127, filed Oct. 4,2017, which claims priority to U.S. Provisional Application No.62/404,009, filed Oct. 4, 2016. The contents of the aforementionedapplications are each hereby incorporated by reference.

FIELD OF THE INVENTION

The present disclosure relates to a thermo-responsive solution and inparticular, a solution suitable for use in an osmosis process that issuitable for separating or purifying solutes and or water from anaqueous solution on a large scale and under energy efficient conditions.

BACKGROUND OF THE INVENTION

U.S. Pat. No. 3,130,156 to Neff is directed to a forward osmosisdesalination process, which describes the use of a 2 molar solution ofammonium bicarbonate being used to draw water from seawater across asemi-permeable membrane. According to Neff, the dilute solution obtainedthat contains the water and ammonium bicarbonate mixture is then heatedto convert the ammonium bicarbonate solute into its constituent gases ofammonia and carbon dioxide. The gases are then released from thesolution to leave behind purified water. It is to be appreciated thatconsiderable amounts of energy are required to vaporise the gases.Additionally, only relatively small quantities of water are purifiedfrom a large volume of seawater meaning that the ratio of energy inputrequired in the process to the yield of purified water obtained is low.This means that this process is not suitable for large scaleapplications.

The Neff concept was further developed and refined by McGinnis, asdescribed in U.S. Pat. No. 7,560,029, into a more energy efficientdesalination process that is scalable. The principle of adding a mixtureof ammonia and carbon dioxide with resultant aqueous species of ammoniumcarbonate, ammonium bicarbonate and ammonium carbamate to adjust theosmotic equilibrium in a forward osmosis process is used in McGinnis.Furthermore, the resultant separated water was purified by heating todrive off ammonia and carbon dioxide. The water separated in thisprocess will still be tainted slightly by ammonia and its presence meansthat an odour will be detectable.

Jessop et. al. in US 2014/0076810 describes a switchable water oraqueous solution and its use. The switchable water or aqueous solutionis formed by adding an ionisable additive comprising an ionisablefunctional group having at least one nitrogen atom. The additive isfurther described as a monoamine, a diamine, a triamine, a tetramine ora polyamine, such as a polymer or a biopolymer. The switchable water oraqueous solution is capable of reversibly switching between an initialionic strength and an increased ionic strength by using a trigger, suchas bubbling with CO₂, CS₂ or COS or treatment with Bronsted acids. Theswitchability of the water or aqueous solution allows for the control ofsolubility or insolubility of various hydrophobic liquids or solvents inthe water or aqueous solution. This provides a means of separatingmoderately hydrophobic solvents from the switchable water. One of thedifficulties with the Jessop work is that is difficult to disassociatethe CO₂ from the amine to achieve the switchable water. Trace amounts ofCO₂ and amine can remain solubilised in the draw solution and heatingand stripping and the kinetics of recovery are slow—of the order ofhours to minutes.

US 2013/0240444 to Jung et. al. describes the use of a temperaturesensitive oligomer, wherein the oligomer has a repeating unit of—C(═O)N(R)₂ (ie an amide functional group) where each R may be linear orbranched or together they form a nitrogen containing heterocycle for useas a draw solution. The oligomer may be used in an osmotic draw solutionfor separating out a solute in an aqueous medium. The draw solute isrecoverable by a phase separation at a temperature greater than or equalto a lower critical solution temperature. The lower critical solutiontemperature (LCST) is the critical temperature below which thecomponents of a mixture are miscible. The word lower indicates that theLCST is a lower bound to a temperature interval of partial miscibility,or miscibility for certain compositions only. In other words, thethermosensitive nature of the oligomer exhibits sharply decreased watersolubility in response to a small increase in temperature leading toprecipitation. At a temperature lower than the LCST the oligomer orpolymers therefrom may be easily dissolved in water, but at temperatureshigher than or equal to the LCST the hydrophilicity of the oligomer orpolymers therefrom may decrease and the hydrophobic interactionspredominate. One of the problems with oligomers and polymers is thatthey are relatively large molecules and large molecules create adiffusion concentration polarisation which lowers effective osmoticpotential of the forward osmosis system by making the draw solution lessdrawable. Relatively large molecules and polymers also rely onprecipitation mechanisms rather than emulsification to recover the drawsolute, necessitating a secondary filtration mechanism that increasessystem cost and complexity.

US 2014/0158621 to Lee at al. also describes a thermo-responsive drawsolute based on a compound or material including at least one amidefunctional group, or a carboxylic acid functional group, that can beapplied to water desalination and purification based on forward osmosis.Similar to Jung above, Lee also describes the use and applicability ofan amide type functional group in a thermo-responsive draw solution andthe reliance on the LCST to effect phase separation of a solute from thedraw solution in a forward osmosis application. One of the problems witholigomers and polymers is that they are relatively large molecules andlarge molecules create a diffusion concentration polarisation whichlowers effective osmotic potential of the forward osmosis system bymaking the draw solution less drawable. Relatively large molecules andpolymers also rely on precipitation mechanisms rather thanemulsification to recover the draw solute, necessitating a secondaryfiltration mechanism that increases system cost and complexity.

U.S. Pat. No. 6,858,694 to Onishi et. al describes a stimuli responsivepolymer derivative which exhibits both a lower critical solutiontemperature and an upper critical solution temperature (UCST), causingits reversible dissolution and precipitation depending on the hydrogenion concentration. The polymers described in '694 also rely on an amidetype functional group that are described as exhibiting keto-enoltautomerisation. One of the problems with polymers is that they arerelatively large molecules and large molecules create a diffusionconcentration polarisation which lowers effective osmotic potential ofthe forward osmosis system by making the draw solution less drawable.

US 2016/0175777 to Ikeda et al. describes an improved forward osmosisapparatus employing a draw solution that utilises an anion and cationsource. In particular the anions are derived from CO₂, ie a substancethat generates anions when dissolved in water, such as carbonic acidanions and or hydrogen carbonate anions. The cation source is an aminecompound, which generates cations when dissolved in water. The drawsolution is broadly described as a solution having a cation source andan anion source. The physical separation of the CO₂ relies on gaseousseparation, which is a relatively complex and energy inefficientprocess. Their preferred amines are fully miscible and have a molecularweight of less than 74.

Despite the efforts described above the draw solutions described remainlargely unsatisfactory, they either rely on expensive components,require considerable energy levels to recover the draw solution or relyon large molecules that are inefficient from a draw solutionperspective. It is an object of the present invention to provide asolution that overcomes these difficulties or to at least provide auseful alternative.

SUMMARY OF THE INVENTION

The present invention is directed to a thermo-responsive solution andits use in osmotic processes.

In one aspect the present invention provides a thermo-responsive osmoticsolution having a lower critical solution temperature in a solventsuitable for use in osmosis comprising:

-   -   a) at least one tertiary amine containing compound; and    -   b) at least one enolisable carbonyl;        wherein in use at least one of the base or the at least one        enolisable carbonyl is immiscible with water at or above 20        degrees Celsius and at 1 atmosphere.

In a further aspect the present invention provides a thermo-responsiveosmotic solution having a lower critical solution temperature in asolvent suitable for use in osmosis comprising:

-   -   a) at least one tertiary amine containing compound; and    -   b) at least one enolisable carbonyl of Formula I,

-   -   wherein    -   c) R₁ and R₂ are independently selected from a —C₁-C₇ alkyl or a        —C₃-C₇ monocyclic; or    -   d) one of R₁ or R₂ is selected from a —O—(C₁-C₇ alkyl) and the        other is selected from a —C₁-C₇ alkyl, or    -   e) R₁ and R₂ together, with the carbonyl of Formula I, form        -   1) a 3-15 membered monocyclic ketone or        -   2) a 3-15 membered monocyclic heterocyclic ketone; or        -   3) acetophenone; and            wherein in use at least one of the base or the at least one            enolisable carbonyl is immiscible with water at or above 20            degrees Celsius and at 1 atmosphere.

In another aspect the present invention provides a method for separatinga first solution including one or more solvents, using athermo-responsive solution as defined above, the method comprising:

-   -   1) bringing the first solution into contact with a        semi-permeable membrane;    -   2) allowing one or more solvents in the first solution to flow        through the semi-permeable membrane from the first solution into        the thermo-responsive solution by osmosis to form a second        solution, wherein the thermo-responsive solution is at a higher        osmotic concentration than the first solution;    -   3) raising the temperature of the second solution to or above        the lower critical solution temperature of the thermo-responsive        solution to cause the thermo-responsive solution to become        immiscible with the one or more solvents from the first solution        that have passed through the semi-permeable membrane; and    -   4) separating the one or more solvents that have passed through        the semipermeable membrane from the immiscible thermo-responsive        solution.

In another aspect the present invention provides a method for separatinga first solution including one or more solvents, using athermo-responsive solution as defined above, the method comprising:

-   -   1) bringing the first solution into contact with a        semi-permeable membrane;    -   2) allowing one or more solvents in the first solution to flow        through the semi-permeable membrane from the first solution into        the thermo-responsive solution by osmosis to form a second        solution, wherein the thermo-responsive solution is at a higher        osmotic concentration than the first solution;    -   3) adjusting the lower critical solution temperature of the        thermo-responsive solution to cause the thermo-responsive        solution to become immiscible with the one or more solvents from        the first solution that have passed through the semi-permeable        membrane; and    -   4) separating the one or more solvents that have passed through        the semipermeable membrane from the immiscible thermo-responsive        solution.

In one embodiment the lower critical solution temperature of thethermo-responsive solution is adjusted by adding one or more tertiaryamine containing compounds as defined, or by adding or more enolisablecarbonyls as defined above or by adding combinations of the one or moretertiary amine containing compounds with the one or more enolisablecompounds.

The foregoing brief summary broadly describes the features and technicaladvantages of certain embodiments of the present invention. Furthertechnical advantages will be described in the detailed description ofthe invention and examples that follows.

Novel features that are believed to be characteristic of the inventionwill be better understood from the detailed description of the inventionwhen considered in connection with any accompanying figures andexamples. However, the figures and examples provided herein are intendedto help illustrate the invention or assist with developing anunderstanding of the invention, and are not intended to limit theinvention's scope.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows schematically an osmotic separation process.

FIG. 2 shows the differential scanning calorimetry (DSC) analysis for atriethylamine plus acetone in water solution demonstrating a change ofenthalpy at 32.25° C., which coincides with the observedsolubility/polarity shift.

FIG. 3 shows the differential scanning calorimetry (DSC) analysis for atriethylamine plus 2-butanone in water solution demonstrating a changeof enthalpy at 24.42° C., which coincides with the observedsolubility/polarity shift.

FIG. 4A-FIG. 4C shows a series of photos showing the observabledifferences of a triethylamine plus 2-butanone in water solutiondemonstrating a change in physical properties of the solution over atemperature range. FIG. 4A shows that at 26.65° C. the base, ketone andwater mixture is miscible. FIG. 4B shows that at 26.89° C. the base,ketone and water mixture has become turbid in appearance as a result ofthe base and ketone mixture becoming an emulsion with water. FIG. 4Cshows that at 27.05° C. the base and ketone mixture are immiscible withwater.

FIG. 5A-5C shows a series of photos showing the observable differencesof a triethylamine plus cyclohexanone in water solution demonstrating achange in physical properties of the solution over a temperature range.FIG. 5A shows that at 15.21° C. the base, ketone and water mixture ismiscible. FIG. 5B shows that at 15.38° C. the base, ketone and watermixture has become turbid in appearance as a result of the base andketone mixture becoming an emulsion with water. FIG. 5C shows that at18.33° C. the base and ketone mixture are immiscible with water.

FIG. 6 shows the transmittance versus temperature plots of various drawsolutions showing a clear change in transmission at the LCST of therespective draw solution.

FIG. 7A shows a plot of the transmittance % versus the temperature curveof a draw solution of TEA:MEK:water (0.5:1.0:5.0 respectively). FIG. 7Band FIG. 7C, respectively, show the first and second derivative plots ofthe transmittance curve shown in FIG. 7A.

FIG. 8 shows a plot of the visual LCST of a draw solution with varyingmolar ratios of TEA in the draw solution versus the molar ratio of TEA.

FIG. 9 shows a plot of the visual LCST of a draw solution with varyingmolar ratios of MEK in the draw solution versus the molar ration of MEK.

FIG. 10 shows schematically the flux experiment setup described below inthe examples.

FIG. 11 shows a plot of the average water flux through a membraneinvolving a TEA-MEK draw solution.

FIG. 12 shows a plot of the average water flux through a membraneinvolving a TEA-cycloppentanone draw solution.

FIG. 13 shows the FTIR spectra of TEA.

FIG. 14 shows the FTIR spectra of MEK.

FIG. 15 shows the FTIR spectra of TEA/MEK in a 1:1 molar ratio.

FIG. 16 shows the FTIR spectra of TEA/MEK/water in a 1:1:5 molar ratio.

DETAILED DESCRIPTION OF THE INVENTION

The following description sets forth numerous exemplary configurations,parameters, and the like. It should be recognised, however, that suchdescription is not intended as a limitation on the scope of the presentinvention, but is instead provided as a description of exemplaryembodiments.

Definitions

In each instance herein, in descriptions, embodiments, and examples ofthe present invention, the terms “comprising”, “including”, etc., are tobe read expansively, without limitation. Thus, unless the contextclearly requires otherwise, throughout the description and the claims,the words “comprise”, “comprising”, and the like are to be construed inan inclusive sense as to opposed to an exclusive sense, that is to sayin the sense of “including but not limited to”.

The term “osmosis” is to be understood as a membrane based separationprocess that relies on the semipermeable character of a semi-permeablemembrane to remove dissolved solutes or to effect separation of asolvent from dissolved solutes, and wherein the driving force forseparation is osmotic pressure. The term “osmotic solution” means asolution that creates osmotic pressure across the semi-permeablemembrane.

The term “about” or “approximately” usually means within 20%, morepreferably within 10%, and most preferably still within 5% of a givenvalue or range. Alternatively, the term “about” means within a log(i.e., an order of magnitude) preferably within a factor of two of agiven value.

As used herein, the term “C₁-C₇ alkyl” refers to a fully saturatedbranched or unbranched hydrocarbon moiety, which may be a straight or abranched chain of a particular range of 1-7 carbons. Preferably thealkyl comprises 1 to 7 carbon atoms, or 1 to 4 carbon atoms.Representative examples of C₁-C₇ alkyl include, but are not limited to,methyl, ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl, iso-butyl,tert-butyl, n-pentyl, isopentyl, neopentyl, n-hexyl, 3-methylhexyl,2,2-dimethylpentyl, 2,3-dimethylpentyl, n-heptyl, and the like. Forexample, the expression C₁-C₄-alkyl includes, but is not limited to,methyl, ethyl, propyl, butyl, isopropyl, tert-butyl and isobutyl. In oneembodiment the C₁-C₇ alkyl group may be substituted with one or more ofthe following groups: -halo, —OH, —CN, —NO₂, —C≡CH, —SH, —C₁-C₇ alkyl,—(C₁-C₇ alkyl)-OH, —NH₂, —NH(C₁-C₇ alkyl), —N(C₁-C₇ alkyl)₂, —O(C₁-C₇alkyl), —C(O)—O(—C₁-C₇ alkyl), —C(O)OH; —C(O)—H, or —C(O)—(C₁-C₇ alkyl).

The term “C₃-C₇ monocyclic” as used herein is a 3-, 4-, 5-, 6-, or7-membered saturated or unsaturated monocyclic ring. RepresentativeC₃-C₇ monocyclic groups include, but are not limited to, cyclopropyl,cyclobutyl, cyclopentyl, cyclohexyl, phenyl and cycloheptyl. In oneembodiment, the C₃-C₇ monocyclic cycloalkyl group may be substitutedwith one or more of the following groups: -halo, —OH, —CN, —NO₂, —C≡CH,—SH, —C₁-C₇ alkyl, —(C₁-C₇ alkyl)-OH, —NH₂, —NH(C₁-C₇ alkyl), —N(C₁-C₇alkyl)₂, —O(C₁-C₇ alkyl), —C(O)—O(—C₁-C₇ alkyl), —C(O)OH; —C(O)—H, or—C(O)—(C₁-C₇ alkyl).

The term “3- to 15-membered monocyclic ketone” refers to a 3- to15-membered non-aromatic monocyclic ring system containing a ketonefunctional group. Representative examples of a 3- to 15-memberedmonocyclic ketone include, but are not limited to cyclopropanone,cyclobutanone, cyclopentanone, cyclohexanone, cycloheptanone,cyclooctanone, cyclononanone, cyclodecanone, cycloundecanone,cyclododecanone, cyclotridecanone; cyclotetradecanone andcyclopentadecanone.

In one embodiment, the 3- to 15-membered monocyclic ketone may besubstituted with one or more of the following groups -halo, —OH, —CN,—NO₂, —C≡CH, —SH, —C₁-C₇ alkyl, —(C₁-C₇ alkyl)-OH, —NH₂, —NH(C₁-C₇alkyl), —N(C₁-C₇ alkyl)₂, —O(C₁-C₇alkyl), —C(O)—O(—C₁-C₇ alkyl),—C(O)OH; —C(O)—H, or —C(O)—(C₁-C₇ alkyl).

The term “3- to 15-membered monocyclic heterocyclic ketone” refers to:(i) a 3- or 4-membered non-aromatic monocyclic cycloalkyl in which 1 ofthe ring carbon atoms has been replaced with an N, O or S atom; or (ii)a 5- to 15-membered non-aromatic monocyclic cycloalkyl in which 1-4 ofthe ring carbon atoms have been independently replaced with a N, O or Satom. Representative examples of a 3- to 15-membered monocyclicheterocyclic ketone having one N, O or S atom include, but are notlimited to oxiran-2-one, thiiran-2-one, oxetan-2-one, oxetan-3-one,azetidin-3-one, thietan-2-one, thietan-3-one, dihydrofuran-2(3H)-one,dihydrofuran-3(2H)-one, pyrrolidin-3-one, dihydrothiophen-3(2H)-one,dihydrothiophen-2(3H)-one, tetrahydro-2H-pyran-2-one,dihydro-2H-pyran-3(4H)-one, dihydro-2H-pyran-4(3H)-one, piperidin-3-one,piperidin-4-one, tetrahydro-2H-thiopyran-2-one,dihydro-2H-thiopyran-3(4H)-one, dihydro-2H-thiopyran-4(3H)-one,oxepan-2-one, oxepan-3-one, oxepan-4-one, thiepan-2-one, thiepan-3-one,thiepan-4-one, azepan-3-one, azepan-4-one, oxocan-2-one, oxocan-3-one,oxocan-4-one, oxocan-5-one, thiocan-2-one, thiocan-3-one, thiocan-4-one,thiocan-5-one, azocan-3-one, azocan-3-one, azocan-4-one, azocan-5-one,azonan-3-one, azonan-4-one, azonan-5-one, oxonan-2-one, oxonan-3-one,oxonan-4-one, oxonan-5-one, thionan-2-one, thionan-3-one, thionan-4-one,thionan-5-one, oxacycloundecan-2-one, oxacycloundecan-3-one,oxacycloundecan-4-one, oxacycloundecan-5-one, oxacycloundecan-6-one,azacycloundecan-3-one, azacycloundecan-4-one, azacycloundecan-5-one,azacycloundecan-6-one, thiacycloundecan-2-one, thiacycloundecan-3-one,thiacycloundecan-4-one, thiacycloundecan-5-one, thiacycloundecan-6-one,oxacyclododecan-2-one, oxacyclododecan-3-one, oxacyclododecan-4-one,oxacyclododecan-5-one, oxacyclododecan-6-one, oxacyclododecan-7-one,azacyclododecan-3-one, azacyclododecan-4-one, azacyclododecan-5-one,azacyclododecan-6-one, azacyclododecan-7-one, thiacyclododecan-2-one,thiacyclododecan-3-one, thiacyclododecan-4-one, thiacyclododecan-5-one,thiacyclododecan-6-one, thiacyclododecan-7-one, oxacyclotridecan-2-one,oxacyclotridecan-3-one, oxacyclotridecan-4-one, oxacyclotridecan-5-one,oxacyclotridecan-6-one, oxacyclotridecan-7-one, azacyclotridecan-3-one,azacyclotridecan-4-one, azacyclotridecan-5-one, azacyclotridecan-6-one,azacyclotridecan-7-one, thiacyclotridecan-2-one,thiacyclotridecan-3-one, thiacyclotridecan-4-one,thiacyclotridecan-5-one, thiacyclotridecan-6-one,thiacyclotridecan-7-one, oxacyclotetradecan-2-one,oxacyclotetradecan-3-one, oxacyclotetradecan-4-one,oxacyclotetradecan-5-one, oxacyclotetradecan-6-one,oxacyclotetradecan-7-one, oxacyclotetradecan-8-one,azacyclotetradecan-3-one, azacyclotetradecan-4-one,azacyclotetradecan-5-one, azacyclotetradecan-6-one,azacyclotetradecan-7-one, azacyclotetradecan-8-one,thiacyclotetradecan-2-one, thiacyclotetradecan-3-one,thiacyclotetradecan-4-one, thiacyclotetradecan-5-one,thiacyclotetradecan-6-one, thiacyclotetradecan-7-one,thiacyclotetradecan-8-one, oxacyclopentadecan-2-one,oxacyclopentadecan-3-one, oxacyclopentadecan-4-one,oxacyclopentadecan-5-one, oxacyclopentadecan-6-one,oxacyclopentadecan-7-one, oxacyclopentadecan-8-one,azacyclopentadecan-3-one, azacyclopentadecan-4-one,azacyclopentadecan-5-one, azacyclopentadecan-6-one,azacyclopentadecan-7-one, azacyclopentadecan-8-one,thiacyclopentadecan-2-one, thiacyclopentadecan-3-one,thiacyclopentadecan-4-one, thiacyclopentadecan-5-one,thiacyclopentadecan-6-one, thiacyclopentadecan-7-one,thiacyclopentadecan-8-one. In one embodiment, the 3- to 15-memberedmonocyclic heterocyclic ketone group may be substituted with one or moreof the following groups -halo, —OH, —CN, —NO₂, —C≡CH, —SH, —C₁-C₆ loweralkyl, —(C₁-C₇ alkyl)-OH, —NH₂, —NH(C₁-C₇ alkyl), —N(C₁-C₇ alkyl)₂,—O(C₁-C₇ alkyl), —C(O)—O(—C₁-C₇ alkyl), —C(O)OH; —C(O)—H, or—C(O)—(C₁-C₇ alkyl). For the avoidance of doubt, the 3-5 memberedmonocyclic heterocyclic ketone does not include any amide groups wherethe ketone enolisable carbonyl group is adjacent a N atom in the cyclicstructure.

The term “halo” as used herein refers to —F, —Cl, —Br or —I.

The term immiscible as used herein, means not fully miscible or capableof forming a single continuous phase with the solvent phase.

The term “an enolisable carbonyl” means a compound that has one or morecarbonyl functional groups and wherein at least one of the carbonylfunctional groups has alpha hydrogens (H_(α)) that may be removed by abase to form an enolate and then an enol as shown in the reaction schemebelow.

It is to be understood that the term enolisable carbonyl as used in thespecification does not include a compound having solely an aldehydefunctional group, a compound having solely a carboxylic acid functionalgroup, a compound having solely an amide functional group, a compoundhaving solely an acyl halide functional group or acetylacetone.

The term enolisable carbonyl, without limitation includes one or more ofthe following: acetone, acetophenone, methylethylketone (2-butanone),cyclohexanone, cyclopentanone, 2-propanone, 2-pentanone, 3-pentanone,4-methyl-2-pentanone, 2-octanone and 3-methyl-2-butanone. In a preferredembodiment the term enolisable carbonyl includes one or more of thefollowing acetone, acetophenone, cyclohexanone, cyclopentanone,2-propanone, 2-pentanone, 3-pentanone, 4-methyl-2-pentanone, 2-octanoneand 3-methyl-2-butanone.

The term “tertiary amine containing compound” is preferably one that isa Lewis base. If the base is a Lewis base, it is envisaged that a Lewisadduct may be formed with the enolisable carbonyl. In one embodiment itis preferred that the tertiary amine containing compound is immisciblewith water at or above 20 degrees Celsius under one standard atmosphereof pressure. The solution may include a combination of more than onetertiary amine containing compound. The tertiary amine containingcompound can be aliphatic, conjugated, asymmetric or cyclic.

Examples of suitable tertiary amines include the following:

In one embodiment the base is selected from a —N(C₁-C₇ alkyl)₃. Inanother embodiment the base is selected from a —N(C₁-C₄ alkyl)₃. In yeta further embodiment the base is —N(C₂ alkyl)₃ (triethylamine).

It will be appreciated that the above listed amines are simple enoughfor production on an industrial scale.

The term “thermo-responsive solution” means a solution that exhibits adrastic and discontinuous change of its solubility with temperature.

The term “lower critical solution temperature” (LCST) means the criticaltemperature below which the properties (optical, conductivity and/or pH)of the solution begin to change on the continuum to the components ofthe solution becoming miscible.

The present invention is directed to a thermo-responsive osmoticsolution and its use in osmosis processes. The inventor has conductedresearch into looking for alternative thermo-responsive solutions thatare likely to be readily scalable on an industrial scale, whilst alsoproviding very efficient diffusion and osmotic potential properties bothcost and energy efficiently. The inventor has determined that a suitablethermo-responsive osmotic solution having a lower critical solutiontemperature in a solvent for use in osmosis comprises:

-   -   b) at least one tertiary amine containing compound; and    -   c) at least one enolisable carbonyl of Formula I,

wherein

-   -   d) R₁ and R₂ are independently selected from a —C₁-C₇ alkyl or a        —C₃-C₇ monocyclic or a -phenyl; or    -   e) one of R₁ or R₂ is selected from a —O—(C₁-C₇ alkyl) and the        other is selected from a —C₁-C₇ alkyl, or    -   f) R₁ and R₂ together, with the carbonyl of Formula I, form        -   1) a 3-15 membered monocyclic ketone or        -   2) a 3-15 membered monocyclic heterocyclic ketone; or        -   3) acetophenone; and            wherein in use at least one of the base or the at least one            enolisable carbonyl is immiscible with water at 20 degrees            Celsius and at 1 atmosphere.

In one embodiment, R₁ and R₂ of Formula I are independently selectedfrom a —C₁-C₇ alkyl. In another embodiment R₁ and R₂ are independentlyselected from methyl and ethyl. In one embodiment the enolisablecarbonyl is selected from 2-butanone, acetone, isobutylketone. In oneembodiment the solution includes a combination of more than oneenolisable carbonyl of Formula I. In one embodiment the combination ofenolisable carbonyls of Formula I includes the following combinations;

-   -   A. 2 butanone and 2-propanone;    -   B. 2-propanone and cyclohexanone;    -   C. 2 butanone and cyclohexanone;    -   D. 2 propanone, 2 butanone and cyclohexanone;    -   E. 2-propanone and 2-pentanone;    -   F. Cyclopentanone and acetophenone;    -   G. Cyclopentanone and 2-octanone;    -   H. Cyclopentanone and 4methyl-2-pentanone;    -   I. 2-butanone, cyclopentanone and 2-propanone; and    -   J. 2-propanone, 3-pentanone and 3-methyl-2-butanone.

In one embodiment the solution includes a combination of more than onetertiary amine containing compound of Formula I. In one embodiment thecombination of tertiary amine containing compounds includes thefollowing combinations;

-   -   K. Triethylamine and 1-ethylpiperidine;    -   L. Triethylamine and diethylmethylamine;    -   M. Triethylamine, diethylmethylamine and 1-ethylpiperidine; and    -   N. Triethylamine, diethylmethylamine and dimethylbenzylamine;

In one embodiment R₁ of Formula I is selected from a —C₁-C₇ alkyl and R₂is selected from a —O—(C₁-C₇ alkyl). In a further embodiment theenolisable carbonyl is selected from ethyl formate or methyl formate.

In a further embodiment wherein R₁ and R₂ of Formula I together form acyclic system selected from a 3-15 membered monocyclic ketone or amonocyclic ester. In one embodiment the enolisable carbonyl is selectedfrom cyclohexanone or tetrahydro-2H-pyran-2-one.

It is to be appreciated that when R₁ and R₂ together form a cyclicsystem, the cyclic system may be further substituted with one or moresubstituents selected from -halo, —OH, —CN, —NO₂, —C≡CH, —SH, —C₁-C₇alkyl, —(C₁-C₇ alkyl)-OH, —NH₂, —NH(C₁-C₇ alkyl), —N(C₁-C₇ alkyl)₂,—O(C₁-C₇ alkyl), —C(O)—O(—C₁-C₇ alkyl), —C(O)OH; —C(O)—H, or—C(O)—(C₁-C₇ alkyl) or the like.

It is to be appreciated that the molar ratio of the base to theenolisable carbonyl of Formula I may vary widely and may be from about1:99 or 99:1; or from about 1:50 or 50:1 or from about 1:10 or 10:1 orfrom about 1:5 or 5:1 or from about 1:3 or from about 3:1 or from about1:2 or from about 2:1. In a preferred embodiment the molar ratio isabout 1:1. A chemistry technician would be able to routinely determinethe most suitable molar ratio depending on the purpose for which thethermo-responsive solution is to be employed. A range of molar ratiosfor various thermo-responsive solutions are shown in FIGS. 7 to 9 .

In one embodiment the solvent is water.

In a further aspect there is provided an osmotic process or method forseparating a first solution including one or more solvents, using athermo-responsive solution as defined above. The method comprises:

-   -   1) bringing a first solution into contact with a semi-permeable        membrane;    -   2) allowing one or more solvents in the first solution to flow        through the semi-permeable membrane from the first solution into        the thermo-responsive solution by osmosis to form a second        solution, wherein the thermo-responsive solution is at a higher        osmotic concentration than the first solution;    -   3) raising the temperature of the second solution to or above        the lower critical solution temperature of the thermo-responsive        solution to cause the thermo-responsive solution to become        immiscible with the one or more solvents from the first solution        that have passed through the semi-permeable membrane; and    -   4) separating the one or more solvents that have passed through        the semipermeable membrane from the immiscible thermo-responsive        solution.

In another aspect the present invention provides a method for separatinga first solution including one or more solvents, using athermo-responsive solution as defined above, the method comprising:

-   -   1) bringing the first solution into contact with a        semi-permeable membrane;    -   2) allowing one or more solvents in the first solution to flow        through the semi-permeable membrane from the first solution into        the thermo-responsive solution by osmosis to form a second        solution, wherein the thermo-responsive solution is at a higher        osmotic concentration than the first solution;    -   3) adjusting the lower critical solution temperature of the        thermo-responsive solution to cause the thermo-responsive        solution to become immiscible with the one or more solvents from        the first solution that have passed through the semi-permeable        membrane; and    -   4) separating the one or more solvents that have passed through        the semipermeable membrane from the immiscible thermo-responsive        solution.

In one embodiment the lower critical solution temperature of thethermo-responsive solution is adjusted by adding one or more tertiaryamine containing compounds as defined, or by adding or more enolisablecarbonyls as defined above or by adding combinations of the one or moretertiary amine containing compounds with the one or more enolisablecompounds.

It is to be appreciated that the first solution in the above aspects mayinclude one or more dissolved solutes. In a further embodiment the firstsolution is selected from seawater, brackish water, industrial waterwaste streams, compromised water sources, sewage, wastewater liquors,digestates, food & beverage processing effluents, grey water, fruitjuices, vegetable juices, milk, produced waters, leachates, flue gasscrubber discharge or the like.

EXAMPLES

The examples described herein are provided for the purpose ofillustrating specific embodiments of the invention and are not intendedto limit the invention in any way. Persons of ordinary skill can utilisethe disclosures and teachings herein to produce other embodiments andvariations without undue experimentation. All such embodiments andvariations are considered to be part of this invention.

Example 1

In a first example, the inventor took equal molar ratios of acetone asthe enolisable carbonyl plus triethylamine as the base in a volume ofwater in a test tube. A DSC scan of that solution showed that there wasa thermo-responsive point at 32.25° C. at which the lower criticalsolution temperature was reached—see FIG. 2 . It was observed that closeto that point the solution went from a miscible mixture ofacetone/tertiary amine in water through an emulsion to an immisciblemixture of acetone/tertiary amine in water.

Example 2

In a second example, the inventor took equal molar ratios of 2-butanoneas the enolisable carbonyl plus triethylamine as the base in a volume ofwater in a test tube. A DSC scan of that solution showed that there wasa thermo-responsive point at 24.42° C. at which the lower criticalsolution temperature was reached—see FIG. 3 . It was observed that closeto that point the solution went from a miscible mixture of2-butanone/tertiary amine in water to an immiscible mixture of2-butanone/tertiary amine in water. A series of photographs shown asFIGS. 4A-C show the observable changes to the solution mixture. It canbe seen in FIG. 4A at 26.65° C. the base and 2-butanone mixture ismiscible. At 26.89° C. the base and ketone mixture has become turbid inappearance (see FIG. 4B) as a result of the base and ketone becoming anemulsion with the water. With a further temperature increase it can beseen in FIG. 4C that at 27.05° C. the base and 2-butanone are immisciblewith the water.

The inventor has determined that the effect observed in the solutions isreproducible. The DSC analysis further determined that thesolubility/polarity shift is an endothermic phenomenon, suggesting thatsome form of enthalpy of fusion is occurring and that the mixing of thecomponents in their soluble state with water is exothermic. It is to berecognised that the different temperature at which thesolubility/polarity switch is seen varies depending on the nature of thecomposition of the thermo-responsive solution. It is to be appreciatedthat over the temperature at which the solubility or polarity switch isseen the ketone base mixture passes from a miscible mixture through anemulsion to a ketone and base mixture that is immiscible with water.

Example 3

In a third example, the inventor took equal molar ratios ofcyclohexanone as the enolisable carbonyl plus triethylamine as the basein a volume of water in a test vials and slowly increased thetemperature of the mixture. A series of photographs shown as FIGS. 5A-5Cshow the observable changes to the solution mixture. The series ofphotographs show the observable differences of a triethylamine pluscyclohexanone in water solution demonstrating a change in physicalproperties of the solution over a temperature range. It can be seen inFIG. 5A at 15.21° C. the base and ketone mixture is miscible with water.At 15.38° C. the base and ketone mixture has become turbid in appearance(see FIG. 5B) as a result of the base and ketone becoming an emulsionwith water and at 18.33° C. the base and ketone are immiscible withwater (see FIG. 5C).

Example 4

It is to be understood that the LCST measured above in Examples 1 to 3was supported by visual changes in terms of visibility or otherwise ofthe immiscible vs miscible layers. The exact point of the optical changecan be difficult to judge visually. It has been found that it is easierto measure the optical properties of various test solutions to determinethe transition of the LCST using a UV-Vis-NIR spectrometer.Transmittance of the test solutions at different temperatures wasrecorded using Stellar Net's SILVER-Nova fiber optic spectrometer whichhas a wide wavelength range of 190-1110 nm. The light source was SL1tungsten-halogen lamps effective for reflectance, transmittance andabsorbance measurements. A dip probe connected the light source and aspectrometer was used to measure the characteristics of the drawsolution.

Materials and Methodology

Various test draw solutions were prepared using triethylamine (TEA),methyl ethyl ketone (MEK), N-ethylpiperidine, diethylymethylamine,cyclohexanone and diethylmethylamine and water various molar ratios andcombinations in a 25 mL glass vial. The transmittance was recorded forevery 2 seconds at a wavelength of 850 nm over varying temperatures.Resistance temperature detector (RTD) probe was inserted along with thedip probe to record the temperatures simultaneous to the episodescaptured every 2 seconds. The main objective was to record a transitionin the transmittance at the LCST where the solution transforms from aclear solution (100% transmittance) below LCST to cloudy above it. Thecontroller used to ramp the temperature at the rate of 2° C./min was aQpod-2e which has Peltier based cuvette holder with magnetic stirring.For one test solution using TEA, MEK and water in the molar ratios of0.5:1:5 (respectively) first and second derivative curves were alsoobtained.

Results

Data from the experiment was used to obtain the transmittance % vstemperature curves at 850 nm as shown in FIG. 6 . FIG. 6 shows thetransmittance curve of the draw solutions recorded at varyingtemperatures at 850 nm. A sharp drop in transmission % was observed forall draw solutions at the LCST. For one test solution using TEA, MEK andwater in the molar ratios of 0.5:1:5 (respectively) a transmission curvewas obtained as shown in FIG. 7A and then first and second derivativecurves as shown in FIG. 7B and FIG. 7C, respectively, were alsoobtained. The inventors are of the view that the point at which thecurve intersects the x-axis at just under 28 degrees C. of the secondderivative curve is to be taken as the LCST for that particular testsolution.

Example 5: Molar Ratio

In a fourth example, the molar ratios of various thermo-responsivesolutions comprising triethylamine and a ketone in water at differenttemperatures were measured and the miscibility of the solution in waterwas recorded. The results are tabulated below in Table 1-4.

TABLE 1 Components water; water; water; triethylamine; triethylamine;triethylamine; water propanone 2-butanone cyclohexanone Mol Ratio 144:0144:6:6 144:6:6 144:6:6  5° C. miscible miscible miscible miscible 20°C. miscible miscible miscible immiscible 50° C. miscible immiscibleimmiscible immiscible

Table 2 shows a table of a range of molar ratios of trimethylamine to2-butanone in 500 μL of water and the observed effect on the aqueousphase at 5° C. and 50° C.

TABLE 2 Mol Ratio Aqueous Phase triethylamine:2- triethylamine2-butanone Water triethylamine 2-butanone (observed) butanone (mol ·L⁻¹) (mol · L⁻¹) (uL) (uL) (uL) 5° C. ** 50° C. **  1 99 0.059 5.797500.0 8.17 491.83 clear turbid  2 98 0.116 5.702 500.0 16.23 483.77clear turbid  3 97 0.173 5.609 500.0 24.19 475.81 clear turbid  4 960.230 5.516 500.0 32.06 467.94 clear turbid  5 95 0.285 5.424 500.039.82 460.18 clear turbid 10 90 0.554 4.983 500.0 77.23 422.77 clearturbid 20 80 1.044 4.177 500.0 145.65 354.35 clear turbid 30 70 1.4823.458 500.0 206.68 293.32 clear turbid 40 60 1.875 2.812 500.0 261.46238.54 clear turbid 50 50 2.229 2.229 500.0 310.90 189.10 clear turbid60 40 2.551 1.700 500.0 355.75 144.25 clear turbid 70 30 2.844 1.219500.0 396.61 103.39 clear turbid 80 20 3.112 0.778 500.0 434.00 66.00clear turbid 90 10 3.358 0.373 500.0 468.35 31.65 clear turbid 95 53.474 0.183 500.0 484.49 15.51 clear turbid 96 4 3.496 0.146 500.0487.64 12.36 clear turbid 97 3 3.519 0.109 500.0 490.77 9.23 clearturbid 98 2 3.541 0.072 500.0 493.87 6.13 clear turbid 99 1 3.563 0.036500.0 496.95 3.05 clear turbid ** stablisation at 5° C. for 30 mins,immersion in 50° C. for 10 seconds, observe

Table 3 shows a table of a range of molar ratios of trimethylamine topropanone in 500 μL of water and the observed effect on the aqueousphase at 5° C. and 50° C.

TABLE 3 Mol Ratio Aqueous Phase triethyl- triethylamine propanone Watertriethylamine propanone (observed) amine:propanone (mol · L⁻¹) (mol ·L⁻¹) (uL) (uL) (uL) 5° C. ** 50° C. **  1 99 0.061 6.084 500.0 8.57491.43 clear turbid  2 98 0.122 5.979 500.0 17.02 482.98 clear turbid  397 0.182 5.876 500.0 25.35 474.65 clear turbid  4 96 0.241 5.774 500.033.56 466.44 clear turbid  5 95 0.299 5.674 500.0 41.65 458.35 clearturbid 10 90 0.577 5.193 500.0 80.48 419.52 clear turbid 20 80 1.0814.323 500.0 150.76 349.24 clear turbid 30 70 1.525 3.557 500.0 212.64287.36 clear turbid 40 60 1.918 2.877 500.0 267.56 232.44 clear turbid50 50 2.270 2.270 500.0 316.62 183.38 clear turbid 60 40 2.586 1.724500.0 360.72 139.28 clear turbid 70 30 2.872 1.231 500.0 400.57 99.43clear turbid 80 20 3.131 0.783 500.0 436.76 63.24 clear turbid 90 103.368 0.374 500.0 469.77 30.23 clear turbid 95 5 3.479 0.183 500.0485.21 14.79 clear turbid 96 4 3.500 0.146 500.0 488.22 11.78 clearturbid 97 3 3.522 0.109 500.0 491.20 8.80 clear turbid 98 2 3.543 0.072500.0 494.16 5.84 clear turbid 99 1 3.564 0.036 500.0 497.09 2.91 clearturbid ** stablisation at 5° C. for 30 mins, immersion in 50° C. for 10seconds, observe

Table 4 shows a table of a range of molar ratios of trimethylamine tocyclohexanone in 500 μL of water and the observed effect on the aqueousphase at 5° C. and 50° C.

TABLE 4 Mol Ratio cyclo- cyclo- Aqueous Phase triethylamine:cy-Triethylamine hexanone Water triethylamine hexanone (observed)clohexanone (mol · L⁻¹) (mol · L⁻¹) (uL) (uL) (uL) 5° C. ** 50° C. **  199 0.048 4.764 500.0 6.71 493.29 clear turbid  2 98 0.096 4.699 500.013.38 486.62 clear turbid  3 97 0.143 4.635 500.0 20.00 480.00 clearturbid  4 96 0.190 4.572 500.0 26.57 473.43 clear turbid  5 95 0.2374.509 500.0 33.10 466.90 clear turbid 10 90 0.467 4.200 500.0 65.09434.91 clear turbid 20 80 0.903 3.612 500.0 125.95 374.05 clear turbid30 70 1.312 3.061 500.0 182.99 317.01 clear turbid 40 60 1.696 2.544500.0 236.55 263.45 clear turbid 50 50 2.057 2.057 500.0 286.95 213.05clear turbid 60 40 2.398 1.599 500.0 334.45 165.55 clear turbid 70 302.720 1.166 500.0 379.31 120.69 clear turbid 80 20 3.024 0.756 500.0421.72 78.28 clear turbid 90 10 3.312 0.368 500.0 461.90 38.10 clearturbid 95 5 3.450 0.182 500.0 481.20 18.80 clear turbid 96 4 3.477 0.145500.0 485.00 15.00 clear turbid 97 3 3.504 0.108 500.0 488.78 11.22clear turbid 98 2 3.531 0.072 500.0 492.54 7.46 clear turbid 99 1 3.5580.036 500.0 496.28 3.72 clear turbid ** stablisation at 5° C. for 30mins, immersion in 50° C. for 10 seconds, observe

Example 6—Ketone and Amine Combinations

In a fifth example, the molar ratios of various thermo-responsivesolutions comprising triethylamine and a mixture of ketones in water atdifferent temperatures were measured and the miscibility of the solutionin water was recorded. The results are tabulated below in Table 5.

TABLE 5 Components water; water; water; water; triethylamine;triethylamine; triethylamine; triethylamine; propanone; propanone;propanone; 2-butanone; 2-butanone; 2-butanone cyclohexanonecyclohexanone cyclohexanone Mol Ratio 144:6:3:3 144:6:3:3 144:6:3:3144:6:2:2:2  5° C. miscible miscible miscible miscible 20° C. misciblemiscible immiscible miscible 50° C. immiscible immiscible immiscibleimmiscible

It can be seen from the tabulated results that combinations of ketonemixtures are equally as effective as a single ketone. It can also benoted that the temperatures at which immiscibility occurs can becontrolled by selection of the components of the ketone mixture.

Minimum Ratios of Amine, Ketones and Water

The following experiments were carried out to determine the minimumratio of amine, ketone and water respectively in the draw solution tobehave as a switchable polar draw solution. The major objective of thisexperiment was to learn how to manage the solution components in themost economical manner. The model draw solution used for this test was acombination of triethylamine (TEA), methyl ethyl ketone (MEK) and water.

Minimum Molar Ratio of Amine

The draw solution was prepared using TEA, MEK and water with the molarratio of TEA varying from 0.1 to 1 in 25 mL glass vials. The quantityand number of moles of TEA with respect to the molar ratio was tabulated(as shown in Table 6). A constant molar ratio of 1:10 for MEK (4.0061 g)and water (10 g) was maintained throughout. For all the test samples,the visual LCST was recorded using a resistance temperature detector(RTD).

TABLE 6 Visual LCST data of the draw solution containing TEA, MEK andwater with varying ratios of TEA Triethylamine (TEA) Number Molar LCSTQuantity of moles ratio (in ° C.) 0.5621 0.0050 0.1 23.7-24.3 1.12430.0100 0.2 24.2-24.5 1.68655 0.0150 0.3 26.6-26.8 2.2487 0.0200 0.427.3-27.5 2.8109 0.0250 0.5 27.6-27.7 3.3731 0.0300 0.6 27.6-27.83.93528 0.0350 0.7 27.6-27.8 4.497467 0.0400 0.8 27.2-27.4 5.059650.0450 0.9 27.2-27.5 5.6218 0.0500 1 27.5-27.8

From FIG. 8 , it can be seen that the LCST increased with an increase inthe molar ratio of TEA from 0.1 to 0.4 in the draw solution. For themolar ratios greater than 0.4, the LCST remained the same. From theseresults the minimum molar ratio of TEA required is 0.5 for the drawsolution to behave as a switchable polar solution without altering theLCST.

Minimum Molar Ratio of Ketone

The draw solution was prepared by using TEA, MEK and water with themolar ratio of MEK varying from 0.1 to 1 in 25 mL glass vials. Thequantity and number of moles of MEK with respect to the molar ratio wastabulated (as shown in Table 7). A constant molar ratio of 1:10 for TEA(5.6218 g) and water (10 g) was maintained throughout. For all thesamples, the visual LCST was recorded using a resistance temperaturedetector (RTD).

TABLE 7 Visual LCST data of the draw solution containing TEA, MEK andwater with varying ratios of MEK. MEK LCST Ratio Quantity(g) Moles (in °C.) 0.1 0.4006 0.0050 19.6-19.8 0.2 0.8012 0.0100 21.2-21.3 0.3 1.20180.0150 22.4-22.6 0.4 1.6024 0.0200 23.7-23.8 0.5 2.0031 0.0250 24.5-24.70.6 2.4037 0.0300 25.3-25.6 0.7 2.8043 0.0350  25.9-26.02 0.8 3.20490.0400 26.4 0.9 3.6055 0.0450 27.1

From FIG. 9 , it can be seen that the visual LCST values are increasingwith an increase in the molar ratios of MEK and there is no point atwhich it stabilises or becomes constant. Thus, for all the draw solutionformulations, the molar ratio of ketone is maintained as 1.

Example 7—Volume Ratios

In a sixth example, the volumetric ratios of the various components of athermo-responsive solutions in water at 20 degrees C. were studied andtheir respective miscibilities in water were recorded. The results aretabulated below in Table 8.

TABLE 8 Components water; water; water; water; water propanone2-butanone cyclohexanone triethylamine Vol Ratio 50:50 50:50 50:50 50:5050:50 20° C. miscible miscible immiscible immiscible immiscible

Example 8—Controls

In a seventh example, the various components of a thermo-responsivesolutions in water at 20, 30 and 50 degrees C. were studied and theirrespective miscibilities in water were recorded. The results aretabulated below in Tables 9 and 10.

TABLE 9 Components water; water; water; triethylamine; triethylamine;water triethylamine 2-butanone 2-butanone 2-butanone 20° C. miscibleimmiscible immiscible miscible miscible 30° C. miscible immiscibleimmiscible immiscible miscible 50° C. miscible immiscible immiscibleimmiscible miscible

TABLE 10 Components water; water; water; triethylamine; triethylamine;water triethylamine propanone propanone propanone 20° C. miscibleimmiscible miscible miscible miscible 30° C. miscible immisciblemiscible miscible miscible 50° C. miscible immiscible miscibleimmiscible miscible

It can be seen from Tables 9 and 10 that the miscibility properties ofthe components can vary significantly depending on the temperature andthe components in the mixture. For example, it can be seen in Table 4that at 20 degrees Celsius (C), both triethylamine and 2-butanone areimmiscible in water. However, at the same temperature, a mixture of bothtriethylamine and 2-butanone in water is miscible, while at 30 degreesC. the mixture becomes immiscible. This exemplifies a thermo-responsivesolution.

Similar results are seen in Table 10, with the exception that in thisexample, the ketone, propanone, is miscible in water, whereas incontrast in Table 9, 2-butanone was immiscible in water.

Multiple Amines and Single Ketone

The compounds being used to prepare switchable polar draw solutions forvarious applications are bases and enolisable carbonyls. Tertiary amineswhich are basic in nature are combined with ketones which are organiccompounds with a carbonyl group and the resulting combinations arechecked for a lower critical solution temperature (LCST). The effect ofconjugation, substitution and addition of functional groups on theswitch point are observed and the data obtained are put to further usedepending on the applications in the future. Ketones are selected suchthat they are in series (for example, 2-propanone, 2-butanone and soon), isomers (for example, 2-pentanone and 3-pentanone), cyclic (forexample, cyclopentanone) and conjugated (for example, acetophenone) innature.

The draw solutions were formulated to consist of multiple amines andketones whilst still exhibiting thermo-responsive properties. Theketones were combined with few selected amines in different molar ratiosand the LCSTs were recorded on addition of water. Several combinationsare described in the following experiment. Additionally, the effect ofdifferent ketone/amine combinations on the osmotic pressure wasobserved.

Instruments

The temperature was varied to determine the LCST using Qpod-2e which isa Peltier based cuvette holder with constant stirring. The visual LCSTtemperature was recorded using resistance temperature detector (RTD)probe. The osmolality of the draw solution at 10% by weight in water wasdetermined by freezing point method based osmometer, Osmomat 3000.

Methodology

The draw solutions were made up with amine(s), ketone(s) and water inthe specified molar ratios and the visual LCST of the draw solution wasdetermined. Visual LCST refers to the temperature at which the solutionturns cloudy just before it separates out into two phases and the LCSTwas recorded using the resistance temperature detector (RTD) probe.

Osmotic pressure of the draw solution was measured for the draw solutionwith 10% pure draw (by weight) in 90% water (by weight). 50 μL of thetest sample (chilled draw solution in single phase) was pipetted outinto the measuring vessel and attached to the thermistor probe of theosmometer. The test draw solution sample measurement was performedautomatically and the osmolality of solute (pure draw) was displayed onthe screen. At least 3 trials were performed on each sample and theaverage was reported.

Types of Combinations

Different types of amines and ketones were combined in differentcombinations such that they would behave as a switchable polar drawsolution. A few draw solution combinations were selected as follows:

-   -   Single amine combined with ketone(s)    -   Multiple amines combined with single ketone    -   Multiple amines combined with multiple ketones        The following abbreviations are used in Tables 11-14:        K1=Ketone 1, K2=Ketone 2, K3=Ketone 3; A1=Amine 1, A2=Amine 2,        A3=Amine 3, TEA=triethylamine, 2-P=2-propanone,        2-PENT=2-pentanone, 3-P=3-pentanone, 2-B=2-Butanone,        CH=cyclohexanone, CP=cyclopentanone, 1EP=1 ethylpiperidine,        DEMA=diethylmethylamine, ACET=acetophenone, 2-O=2-octanone,        4M2P=4-Methyl-2-pentanone, 3M2B=3-methyl-2-butanone,        DMBA=dimethylbenzylamine.

The following Table 11 summarises the LCST and the osmotic pressure ofdifferent combinations of draw solutions containing a single amine withone or more ketone(s): Note: the osmotic pressure is at 10% of pure drawby weight.

TABLE 11 Molar ratio Visual Osmotic of LCST pressure A1 K1 K2 K3amine:ketone:water (° C.) (mOsmol/kg) TEA 2-P — — 6:6:144 45 923.67 TEA2-B — — 6:6:144 27 1350 TEA CH — — 6:6:144 11.5 905.33 TEA 2-B 2-P —6:3:3:144 28.3 1251.000 TEA 2-P CH — 6:3:3:144 22.8 710.000 TEA 2-B CH —6:3:3:144 20.5 1020.333 TEA 2-P 2-B CH 6:2:2:2:144 25.3 1097.333Combination of Multiple Amines and Single Ketone

The following table 12 summarises the LCST and the osmotic pressure ofcombinations of draw solutions containing multiple amines with a singleketone: Note: the osmotic pressure is measured at 10% of pure draw byweight.

TABLE 12 Osmotic pressure Molar ratio VisualLCST (mOsmol/ A1 A2 A3 K1amines:ketone:water (° C.) kg) TEA 1-EP — 2-B 0.5:1:10 22.7 1114 TEADEMA — 2-B 0.5:1:10 35.8 1150.3 TEA 1-EP DEMA 2-B 0.5:1:10 31.3 1258.3TEA 1-EP — CP 0.5:1:10 22.7 1098.67 TEA DEMA — CP 0.5:1:10 32 1054 TEA1-EP DEMA CP 0.5:1:10 41.6 1180.3Combination of Amine(s) and Two Ketones

The following table 13 summarises the LCST and the osmotic pressure ofcombinations of draw solutions containing one or more amine(s) with twoketones: Note: the Osmotic pressure is at 10% of pure draw by weight.

TABLE 13 Molar ratio Visual LCST Osmotic pressure A1 A2 K1 K2amine(s):ketone(s):water (° C.) (mOsmol/kg) TEA — 2-P 2-PENT 0.5:1:1035.7 1323.3 1-EP — 2-P 2-PENT 0.5:1:10 22.5 1284.3 TEA 1-EP 2-P 2-PENT0.5:1:10 31.9 1181 TEA — CP ACET 0.5:1:10 15.6 1017 1-EP — CP ACET0.5:1:10 6.5 995 TEA 1-EP CP ACET 0.5:1:10 10.5 993.67 TEA — CP 2-O0.5:1:10 6.7 1006.6 1-EP — CP 2-O 0.5:1:10 0 840.6 TEA 1-EP CP 2-O0.5:1:10 1.5 868 TEA — CP 4M2P 0.5:1:10 13.1 1141 1-EP — CP 4M2P0.5:1:10 9.5 1013.3 TEA 1-EP CP 4M2P 0.5:1:10 12.3 1059.3Combination of Amine(s) and Multiple Ketones

The following table 14 summarises the LCST and the osmotic pressure ofdraw solutions containing combination of one or more amine(s) withmultiple ketones:

TABLE 14 Molar Osmotic pressure at ratio of Visual LCST 10% of pure drawby A1 A2 A3 K1 K2 K3 A(s):K(s):water (° C.) weight (mOsmol/kg) TEA — —2-B CP 2-P 0.5:1:10 30.5 1096.33 1-EP — — 2-B CP 2-P 0.5:1:10 29.31172.67 TEA 1-EP DMBA 2-B CP 2-P 0.5:1:10 24 993.67 TEA — — 2-P 3-P 3M2B0.5:1:10 15.2 1107 1-EP — — 2-P 3-P 3M2B 0.5:1:10 5.6 972 TEA 1-EP DMBA2-P 3-P 3M2B 0.5:1:10 −1 983

From these results it can be appreciated that effective LCST drawsolutions can be prepared from a number of amines and ketones in variouscombinations and ratios. The results also show that a very wide spreadof different temperature LCST draw solutions can be obtained and that adesired temperature of a LCST draw solution could be achieved by usingdifferent amines and ketones. It is also to be appreciated that if theLCST of a given draw solution is too high or too low, the LCST could bemodified by adding a ketone or an amine. It can also be seen from theresults that significant osmotic pressure readings are obtained with anumber of these draw solutions.

Example 9—Flux Experiment

The flux of water across a semipermeable membrane using draw solutionsof the present invention (as detailed in Table 15) have been studiedusing a test system as illustrated in FIG. 10 . The test systemcomprises a gear pump (1) that is used to circulate the feed from thefeed tank (3) into the membrane cell (4). A conductivity probe (2) isused to measure the conductivity in the feed tank (3). Three way valve(5) on the feed side of the membrane cell (4) and three way valve (6) onthe draw side of the membrane cell (4) are used to isolate the membranecell when cleaning or replacing the membrane. Another valve (7) is usedto isolate the draw side when maintenance is required. This valve (7)can also be used then cleaning or replacing the membrane. A gear pump(8) on the draw side is used to circulate the draw solution into themembrane cell. A resistance temperature detector (9) is used to controlthe temperature after the chiller (10), which is a heat exchange used tocoll the draw solution before entering the membrane cell (4). A filter(11) is shown that allows the flux experiment to be run at atmosphericpressure without exposing the operator to vapors or fumes. A coalescercartridge (12) is used to collect the draw solution and water after themembrane cell (4). A draw tank and coalescer (13) are used forseparation of the draw solution from water. At the bottom of the drawtank and coalescer (13) is a valve (1) that is used to drain thetank/coalescer. A resistance temperature detector (15) is used tocontrol the temperature after the heater (16), which is a heat exchangerused to heat the draw solution before being returned to the draw tankand coalesce (13). Two way valve (17) is used to isolate the draw sidewhen cleaning or replacing the membrane. Three way valve (18) on thedraw side of the membrane cell (4) and three way valve (19) on the drawside of the membrane cell (4) are used to isolate the membrane cell whencleaning or replacing the membrane. Two way valve (20) is used toisolate the feed side when cleaning or replacing the membrane. The testsystem was flushed with deionised water (in triplicate) on each side ofthe semipermeable membrane in the membrance cell (4). The semipermeablemembrane was a forward osmosis membrane. The feed side of the membranecell was filled with deionised water and the draw side of the membranecell was filled with the selected draw solution being tested. The feedsolution pump (1) and draw solution pump (8) were then turned onsimultaneously and the test system was left to equilibrate for 2-3minutes. The water level in the draw tank (13) was recorded and then thesystem was allowed to operate for 10 minutes. The draw tank (13) wasthen emptied by removing the water down to the originally noted level inthe draw tank and the water was weighed to determine the quantity ofwater that crossed that membrane in 10 minutes. These last two stepswere repeated for the duration of the test. The ratios, drawconcentrations and duration of the tests conducted are tabulated belowin Table 15.

TABLE 15 Ratio Average (amine- Draw Sampling flux Draw Feed ketone) ConcDuration frequency (l/h/m²) TEA - Deionised 0.5-1.0 10 and 1 h 10 SeeFIG. MEK Water 20% 40 min minutes 11 150 mM See FIG. NaCl aq. 11 TEA -Deionised 0.5-1.0 10 and 1 h 10 See FIG. CP Water 20% 40 min minutes 12150 mM See FIG. NaCl aq. 12 TEA - Deionised 0.5-1.0  5% 1 h 10 1.63 CPWater minutes TEA- Deinonised 1.0:1.0 100%  1 h 10 3.733 MEK water 40 mmminutes CP = cyclopentanone

It can be seen from Table 15 and FIG. 11 and FIG. 12 that the averagewater flux was affected by temperature and draw solution concentration.The highest water flux rate was seen with a 1.0:1.0 ratio of TEA to MEK.In the case of TEA and MEK, as the temperature increased so did thewater flux. As the draw solution concentration doubled the water fluxdropped slightly. In contrast with the TEA cyclopentanone draw solution,the water flux increased when the draw solution concentration doubled.

FTIR Experiments

The draw solutions were analyzed using the FTIR spectrometer. Variousratios of MEK and TEA with water were measured using FTIR. The resultingspectra were then analysed using principal component analysis. Thesamples investigated were labelled as TEA, MEK, TEA:MEK and TEA:MEK:H₂O.

Samples were placed into a sample dish on a temperature control stageand analysed. FT-IR spectroscopy was performed using a Bruker Vertex 70FT-IR spectrometer. Analysis of samples involved obtaining 16 scans toproduce each spectrum and a spectral resolution of 0.4 cm⁻¹.

The resulting spectra are shown as FIG. 13 , FIG. 14 , FIG. 15 and FIG.16 . it can be seen that the carbonyl peak at around 1712-1719 cm⁻¹ isconverted to an enol in the presence of water. The single carbonyl peakat 1712-1719 cm⁻¹ (see in FIG. 14 and FIG. 15 ) is spilt into a doublepeak at 1645-1701 cm⁻¹ representing the enol form.

It is to be appreciated that these solutions that exhibitthermo-responsiveness have applicability as draw solutions in osmoticprocesses. It is to be appreciated that a thermo-responsive solution ofthe present invention could be used as a draw solution in osmoticprocesses as illustrated in FIG. 1 and FIG. 6 . The draw solution can beused, for example, to draw water that requires purification through asemi-permeable membrane into the draw solution. Once the draw solutionhas reached its osmotic potential the draw solution mixture can beheated to its lower critical solution temperature at which point theketone and amine mixture becomes immiscible in the water solution andthe purified/treated water solution can be readily separated (byphysical or mechanical separation in a very energy efficient manner)from the draw solution. The draw solution can be recycled and reused ina further osmotic cycle. It is to be appreciated that the lower criticalsolution temperature can be varied depending on the ketone/amine mix andwhether one or more ketones or amines are used. For energy efficientpurposes it would be desirable to have a lower critical solutiontemperature that is not much higher than room temperature.

The present invention and its embodiments have been described in detail.However, the scope of the present invention is not intended to belimited to the particular embodiments of any process, manufacture,composition of matter, compounds, means, methods, and/or steps describedin the specification. Various modifications, substitutions, andvariations can be made to the disclosed material without departing fromthe spirit and/or essential characteristics of the present invention.Accordingly, one of ordinary skill in the art will readily appreciatefrom the disclosure that later modifications, substitutions, and/orvariations performing substantially the same function or achievingsubstantially the same result as embodiments described herein may beutilized according to such related embodiments of the present invention.Thus, the following claims are intended to encompass within their scopemodifications, substitutions, and variations to combinations, kits,compounds, means, methods, and/or steps disclosed herein.

Accordingly, one of ordinary skill in the art will readily appreciatefrom the disclosure that later modifications, substitutions, and/orvariations performing substantially the same function or achievingsubstantially the same result as embodiments described herein may beutilised according to such related embodiments of the present invention.Thus, the invention is intended to encompass, within its scope, themodifications, substitutions, and variations to processes, manufactures,compositions of matter, compounds, means, methods, and/or stepsdisclosed herein.

The invention claimed is:
 1. A thermo-responsive osmotic solution havinga lower critical solution temperature in a solvent, thethermo-responsive osmotic solution comprising: a) at least one tertiaryamine containing compound selected from:

and b) at least one enolisable carbonyl compound selected from acetone,acetophenone, methylethylketone (2-butanone), cyclohexanone,cyclopentanone, 2-propanone, 2-pentanone, 3-pentanone,4-methyl-2-pentanone, 2-octanone and 3-methyl-2-butanone, or acombination thereof; wherein the at least one tertiary amine containingcompound or the at least one enolisable carbonyl compound is immisciblewith the solvent at or above 20 degrees Celsius and at 1 atmosphere; andwherein the solvent is water.
 2. The solution as claimed in claim 1,wherein the solution comprises a combination of more than one tertiaryamine containing compound.
 3. The solution as claimed in claim 1,wherein the at least one tertiary amine containing compound in thesolution is immiscible with the solvent at or above 20 degrees Celsiusand at 1 atmosphere.
 4. The solution as claimed in claim 1, wherein theat least one tertiary amine containing compound is N(C₁-C₇ alkyl)₃. 5.The solution as claimed in claim 1, wherein the at least one tertiaryamine containing compound is N(C₁-C₄ alkyl)₃.
 6. The solution as claimedin claim 1, wherein the at least one tertiary amine containing compoundis N(C₂ alkyl)₃ (triethylamine).
 7. The solution as claimed in claim 1,wherein the molar ratio of the at least one tertiary amine containingcompound to the at least one enolisable carbonyl compound of Formula Iis about 1:5 or 5:1.
 8. The solution as claimed in claim 1, wherein themolar ratio of the at least one tertiary amine containing compound tothe at least one enolisable carbonyl compound of Formula I is about 1:3or 3:1.
 9. The solution as claimed in claim 1, wherein the molar ratioof the at least one tertiary amine containing compound to the at leastone enolisable carbonyl compound of Formula I is about 1:2 or 2:1. 10.The solution as claimed in claim 1, wherein the molar ratio of the atleast one tertiary amine containing compound to the at least oneenolisable carbonyl compound of Formula I is about 1:1.
 11. The solutionas claimed in claim 1, wherein the at least one tertiary aminecontaining compound is triethylamine and the enolisable carbonyl ismethylethylketone (2-butanone).
 12. The solution as claimed in claim 11,wherein the molar ratio of the triethylamine to methylethylketone(2-butanone) is 1:2.
 13. The solution as claimed in claim 12, whereinthe molar ratio of the triethylamine to methylethylketone (2-butanone)is 1:2.
 14. A thermo-responsive osmotic solution having a lower criticalsolution temperature in a solvent, the thermo-responsive osmoticsolution comprising triethylamine and methylethylketone (2-butanone),wherein the triethylamine or the methylethylketone (2-butanone) isimmiscible with the solvent at or above 20 degrees Celsius and at 1atmosphere; and wherein the solvent is water.